1. Field of the Invention
The present invention relates generally to electron beam imaging apparatus and methods of using same.
2. Description of the Background Art
Automated inspection and review systems are important in process control and yield management for the semiconductor and related microelectronics industries. Such systems include optical and electron beam (e-beam) based systems.
In the manufacture of semiconductor devices, detection of defects early on in the development and fabrication process is becoming increasingly important to shorten product development cycles and increase manufacturing yield. Advanced wafer inspection and review systems based on scanning electron microscopy technology are being used to detect, review and classify defects and feed the root cause information back into the manufacturing process to prevent these defects going forward. The size of relevant defects is directly proportional to the design rule being applied to the manufacturing of the semiconductor devices. As the latter continues to shrink the performance demands on wafer inspection and review SEMs increases both in terms of imaging resolution, elemental analysis capabilities, and speed (defects processed per hour).
With the decreasing size of defects, resolution limiting effects such as charging of the wafer surface become increasingly more performance limiting. Focus, distortion and contrast variations caused by uneven charge distribution can make e-beam inspection, review and classification unstable or even impossible. In order to successfully inspect and review a wafer it is therefore highly advantageous to be able to control any surface charging.
It is desirable to improve e-beam inspection and review apparatus. In particular, it is desirable to better control effects of charging and discharging on images used for inspection and review.